Liquid clarification



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`E. M. 'KELLYA Erm.

LIQUID GLARIFICATION Griginal Filed June 2l, 1941 Dec. 4, 1945.

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-lnri'ginal Filed .Jun-e' 21, 1941 2 Sheets-Sheet 2 Num :.Qvfa/ yv04m,... L w Y c u 0 x mi .imm NMPP?. A /v/ ard 5PZ rf inw@ RUM .Q

Reuma Dee. 4, i945 y 22,701 n LIQUID cLAmFrcA'rIoN Earl M. Kelly and4Arthur M. Kivarl, Los Angeles,

, Calif., Robert P.

Kite, Larchmont, N.

Elliott J. Roberts, Westport, Conn., and David B. Sutherland, Montclair,N. J., assignors to The` Dorr Company, a corporation of DelawareOriginal No. 2,324,400, dated July 13, 1943, Serial.v No. 399458, June21, 1941. Application for reissue August 28, 1945, Serial No. 613,122

13 Claims.

This invention relates to the clarification or purification of liquidsand especially those that are impure or polluted such as sewage, tradeand vdairy wastes, packing and cannery wastes, oil

renery wastes, and the like 'that are character-- ized in that someconstituents/thereof must be removed from the water before it can beeither re-used or released into water-courses like rivers and streams,or into the'ocean.

Such constituents may comprise any particles of turbidity that interferewith the clarity of the water and also particles of matter of organicorigin which is not removed from the water would cause its pollution.Such constituents, in general, exist in the waste waters in the form ofsuspended matter whose settleability ranges from normally readilysettleable solids such as grit, up through varying degrees of .normallysemi-iloatability and difficult settleability to colloids and oil orgrease that are normally nonsettleable.

So one object of this invention'is to devise an improved method andapparatus for the efllcient removal by reduced pressure flotation ofiloatable or suspended matter from liquids that contain them. Suchliquids are well exemplified by sewage. Sewage is treated usually byinowing it is another object of this invention tovdevise equipment forthe clariilcation thereof that isl covered whereby the liquid beingtreated is maintained out of view. V

-A still further object of this invention is to cause certain normallynon-iloatable suspended solids to be floated with a concurrentimprovement in settling the non-floatable and normally settleablesuspended solids.

20 ed is sub-atmospheric, namely, under the effect The invention ispreferably embodied in equipment wherein the polluted liquid has gasdii-l fused therein, called hereafter gassed liquid; 'the gassed liquidis conducted' to, 'and released in proximity to the surface of. a bodyof liquid being treated, on the surface of which liquid there iseffective a pressure that is less than that on the gassedliquid.Normallythe gassed liquid is supplied under atmospheric pressure whilethe pressure on the surface of the liquid being treat- A of vacuum.Moving means are provided for skimming floated matter, including scum,foam,'oil or grease, into an arrangement that includes a dam over whichthe floatingy matter is removed g5 from the zone of treatment of theliquid.

Important in such an arrangement is the control for maintaining of aconstantliquid level it to relatively large settling basins often calledsedimentation tanks or clariilers. Sewage is held in them in quiescenceso that those suspended solids that will settle, do settle and depositon the bottom ot the clarier as sediment. Mechanical means are. usuallyprovided for raking the sediment from the tankv bottom to discharge.These clariers have the'slze controlled by the overflow rate anddetention time necessitated by the settling rates of the suspendedsolids .to be settled. This makes these clarier tanks relatively large,in some cases a hundred or more feetin diameter. Some of the suspendedmaterial is iloatable, which tends to rise to the surface of the liquidin the clarifier and form into a disagreeable scum. The skimming or suchtanks has presented a serious mechanical problem.

Therefore another object of this invention is to devise equipment thatwill remove settleable matter from polluted liquids rapidly and withoutthe necessity of the usual long detention perind, whereby the equipmentcan be made substantlally smaller. And a further object is to arrangesuch equipment so it will also remove for the body of liquid beingtreated, and preferably it should be adjustable. In the preferredembodiment of this invention, this is accomplished by maintaining inwhat may be called a control box, a relatively small or minor body ofliquid being treated apart from the main body so esto be substantially-free from scum or floating solids but in hydraulic communicationtherewith at the bottom portion while in gaseous com'- munication at itstop .portion with the gaseous but reduced pressure atmosphere overlyingthe f liquid being treated.

noatable matter as scum about as fast as accumulated on of theliquid.

Sewage and the like polluted liquids are usu- 'ally either unsightly orodorlferous, 'or both, so

`'Another characteristic oi' this invention is that associated with the.minor or auxiliary body of liquid in the control bbx,l there aresuction-applying means primarily for applying the effect of vacuum tothe main body oi liquid which'automatically lcease applying lsuctionwhen excess liquid accumulates above the desired liquid level. Thesemeans are exemplied by a suction pipe' orunozzle connected' to a` wetvacuum pump. and the .pipe may also be pivotally adjustable forcontrolling the height of vthe controlled liquid level.V Clarined ortreated liquid is removed fromthe equipment in quantity equal to theliquid incoming thereto for treatment, so the machine is continuous inoperation. Also, the clariiled liquid that is removed, is .derived-froma zone ot materially lessened elect of 'vacuum and also from a placewhereat the withdrawn liquid is shielded from descending of settlingsolids.

The sequential gassing and vacuum, or reduced pressure, treatment seemsto cause not only the normally oatable matter but importantly asubstantial quantity of normally non-fioatable and normally diilicultlysettleable suspended solids, as

well as semi-heating solids, to rise or to be buoyed to the liquidsurface from whence they are removed by the skimming means. Othersuspended solids seem to have their settleability increased, so that asa. result of the vacuum treatment, solids from some liquids settle tothe bottom of the tank and deposit as sediment, whereupon they areindependently removed. When treating some liquids, the clarified liquidcan be removed from the tank through the vacuum suction pipe, while intreating other liquids, it may be desirable to remove the treated liquidfrom another zone or zones of the tank.

Since it has been found that the vacuum is ef-A fective to the maximumto float suspended solids substantially only when they are exposed tothe vacuum elects at the liquid surface, it is important thatthevelocity of the suspended solids fed to the machine shall be suchthat solids reach the region of the liquid surface of the body of liquidbeing treated. To this end, the liquid to be treated is' preferablysupplied to the tank by means of a draft tube that is so calibrated andso shaped that the suspended solids in the feed passing up` through thedraft-tube are emitted therefrom into that zone in which the vacuumbecomes effective on them. The design and shape of the draft-tube shouldbe such as to give a velocity of the feed liquid up the draft-tube sothat there is discouraged any dropping back down in the draft-tube ofsettling solids because oncethey start downwardly, the pull of thevacuum is not very strong on them. At the same time.

` this is that it causes the bubbles. buoying up the floated solids tobe shaken loose therefrom, whereupon those solids descend and thusescape being is best. Therefore, that latter ngure is recommended. Ittakes 13:6 inche'sof water to equal one inch of mercury. Therefore, inorder to I have at least some degree of vacuum effective on all theliquid in the tank. except of course that' .v on the bottom thereof, thetank should be of 65 the order of 9 x 13.6 inches indepth, or roughly 10feet. In such a tank,while there is vacuum equal to about 9 inches ofmercury effective on the liquid level in the tank, at one foot below theliquid level, the vacuum equals labout 8 inchesl of mercury, and so ondown. each foot -of -depth taking oil about one mercury inch ofeffectivevness of the vacuum. Beyond flveffeet (or 5 mer? cury inches),however, there seems to be little vacuum effect. but this is desirablefor it leaves that zone of liquid below the five foot level, in relativequiescence in which those solids of high specific gravity settlingthereto, are permitted unmolestedly to form a sediment on the tankbottom, from which they can be removed as desired. 'I'he point of theirwithdrawal is preferably from a region within the treatment tank that isunder the effect of vacuum equal to five inches or less of mercury,because this assures no floating material being carried oil with thesediment. Discharge of materials from such a machine naturally has to bethrough the medium of a liquid-sealed barometric or hydrostatic leg orits equivalent, for otherwise the effect'of vacuum would be lost byair-leakage.

It is generally desirable that nothing be interposed between the liquidlevel and the effect of the vacuum that interferes with theeffectiveness of the vacuum. In order to keep the liquid level clean andclear of vacuum-obstructing material, this invention teaches that it isadvisable to remove fromthe liquid level scum or other oating material(sometimes calledherein fioat) about as fast as formed so that there isno adverse accumulation thereof, and with the least disturbance of theunderlying liquid. In order to accomplish this persistent andnon-turbulent cleaning of the liquid level, it is also necessary tomaintain the liquid level at a constant height so that floating materialcan be constantly and eiectivelyremoved therefrom, Where skimming isimportant of itself, the character of the scum may be controlledsomewhat by the height of the liquid level as compared with theelTective level of the overflow Weir or dam of the scum dischargearrangement. If for instance, a material being handled forms a thickcompactscum and it is desired to discharge this scum with a minimum ofwater-content, then the liquid level of the tank can be lowered to anelevation several inches below the scum overflow Weir independent of thescum discharge arrangement, through the medium of control features ofthe auxiliary compartment or control box with its adjustable suc- 45tion nozzles. If on the other hand, the n handled does not form acompact scum water content is unimportant, the liquid vation of the tankcan then be adju point from which most or all of the oat i.

by gravity over the dam into the scum discharge v outlet. One purpose ofgetting the scum or float out as soon as possible is so that the airbubbles attached to the solids arenot detached, for if detached in anysubstantial quantity, the buoyed up solids will settle and go out withthe emuent.

The flotation effects attained by this vacuum treatment on suspendedsolids take place within a rather limited range of degrees of vacuum, soasl much as possible of the floatable material must 60 assuredly beconveyed into that horizontal layer of liquid'subject to such vacuum.This is assisted to some extent by rst diiusingv dissolving air or gasin the liquid fed to the vacuum tank whereby when the suspendedparticles encounter the lessened pressure in the tank. the dissolved andentrainedgas is released to form gas bubbles that attach themselves tosolid particles and tend Ato float most of the suspended material intothat area of limited vacuum effect. Aeration or gassing of the liquidlprior to its release into body of liquid being treated under the eiectof vacuseless for the notation function. large bubbles are detrimentalbecause they cause undue agitation on being released.

facilitates the subsequent sedimentation.

prior to its release in the liquid body in order to remove from itsubstantially all large or coalesced bubbles. Rising vbubbles enlarge inascending, and an expanding bubble tends to detach itself from the solidthat is buoying up or floating.

` Therefore, the ilner or-smaller the bubbles developing from the liquidunder vacuum the better, for merely large entrained air bubbles'v are Infact the the 1ers-behind non-acatabie and semeabie solids can assumetheir normal free settling rates.

'l'husin a machine embodying this invention, settleable solids settlebetter. The vacuum and the rising force exerted by the air bubbles onthe suspended solids act like a collector, especially when there aregrease or other foamor frothforming substances present, as is especiallytrue i'n sewage and the like wastes. The vacuum apparently has ade-aerating effect. For instance, it makes activated sewage sludge sink.It has a depressant eifect on settleable solids, although not on slicksolids. This type of action resulting from the eifect of vacuum, whensewage and the like are treated, iioats grease-bearing particles andother floatable material away from 'the settleable inorganics, so thatthe sediment separated and discharged by the apparatus of this inventionis fairly clean. The vacuum will cause to float normally non-floatableinorganic matter of some types such as lime sludge derived from watersoftening, as magnesium hydroxide, borax, potash and the like. l

With respect to the treatment of sewage, lit is to be recalled thatsewage coming to a treatment plant at times has a relatively hightemperature. This, together with fiat sewer grades and long flow lines,often results in considerable anaerobic bacterial action taking place inthe sewage prior to clarification treatment, with the result that thereare usually present inthe incoming sewage substantial 1 quantities of.gas bubbles, buoyed scum, and floating, partially-digested sewagesludge. 'I'he discharge of large quantities of cannery wastes intosewerage systems aggravates this problem and increases the floatingscum. 'I'he apparatus of this invention is quite effective von theseconditions, forinot only are the vscum and the sludge separated, butthesewage being treated in the machine is de-gassed.

I'he presence of finely-divided gas' bubblesin sewage or otherliquid hasa Vdecidedly detrimental effect on clarification by sedimentation; so torid the sewage of its entrained gas, substantially .And again, as sewage'and the like wastes are usually highly odorous, the vacuum removal oithis invention ridsthe liquid of its entrained gases and thereby reducestheir odor-giving content.

The trade-mark Vacuator" has been given to and used in connection withembodiments of this invention, prior to the tiling of this application,so that termfor'short, may be used hereinafter.'

A maior characteristic of a Vacuator is the vacnum removal from liquidsnot only of normally iioatable matter but also of normally non-float-'able matter. -A further characteristic is the simultaneous independentremoval from liquids of Thus it is a machine that accomplishes removalIn some cases, the Vacuator`may be used as a by one path, while b yanother path there is passed from the Vacuator, de-scummed liquid withnon-iloatable solids unremoved from suspension therein. O ther uses maycall for three separate discharge paths leading from the Vacuator namely(l) for scum, (2) for clarifier eiiiuent, and (3) for sediment orsludge. The Vacuator has yproven that it can do a fair joh of removingsuspended solids at as high an overflow rate as 10,000 gallons per sq.ft. per 24hours.

Fig. 1 is a vertical sectional view of a continuous type of apparatusfor separating and remov' ing of suspended matter from a liquid body. Inconnection withthis gure itis to be noted that a large main separatingtank prominently appears and that a small or auxiliary liquid-levelcontrol tank or chamber is shown at the righthand side of the largemaintank.

lary liquid-level control tank or chamber. In Fig. 2 the parts are shownat a larger scale than in Fig. 1. y

Fig. 3 is a horizontal sectional view taken -as on the line 3-3 of Fig'.2 looking in the direc? tion of the arrows.

' Fig. 4 is a plan-view o f the apparatus of Fig. 1. In this ligurevcertain vparts of the top of a main separating tank thereof have Abeenbroken away to show more clearly the construction of certain functionalparts therein.

In the accompanying drawings; i0 represents 'a main tank, Il its bottomor floor, I2 its closed roof or top, |32. scum discharge duct o'rpathway elongated edge, dam or weir that is not normally submerged, I6a.l funnel section of the scum discharge duct I3 that supports the weirI5 and a ramp Il leading up to the weir. IH represents '45 an upstandingdraft-tube, I! a feed inlet pipe or conduit of which the draft-tubeforms a func'- tional terminal. 2|) represents a flared outlet sectionof the draft-tube IB, 2| a spider therein by which the draft-tube issupported from shaft 5022 rotatably penetrating, in a gas-tight man-4ner, the tank roof I2, which shaft is provided with a worm gear 23 thatis'rotated Aby a worm 24, driven by a motor 25. 2B indicates scum rakingarms, extending substantially radially from the shaft 22, and A2'Iindicates scum sweeps carried by the arms 28`that are adapted for scumalso for controlling the height of the liquid ,level L in the main tank.3l indicates a freely com' 55 municating passageway provided by a pipeextending between the upper section of the main tank and the uppersection'of the auxiliary or secondary tank Il; 32 indicates a closed topor roof on the secondary tank 30, while 33 indicates a liquid pathway orcommunicating pipe extendingbetweenthebottomilofthetanklandto theinterior liquid-holding portion of the main l5 indicates a wet-vacuumpumpingmeans 75|uchngairorgasfromtheinteriorofthosec-- pended matterdesired to be removed therefrom. Y

skimmer only, so that scum is discharged from it Fig. 2 is a verticalsectional view of the auxil. y

having a barometric or hydrostatic leg Il, l5, ank

free of scum accumulations thereon.

ondary tank 30 by such conduit means as a pipe 36 that terminates in anadjustable inlet end or nozzle 31. Pipe 36 and nozzle 31 can beduplicated as shown. 1f duplicated both -pipes 36 will merge into asingle pipe 38 leading to the pump 35. The inlet ends or nozzles 31 arepivotally adjustable by means of hand-operated shafts 39 that extendthrough the casing of the second tank 30. 4|) indicates a valve that canbe inserted in each suction pipe 36. 4I indicates a discharge pipe lineextending from the vacuum pump 35, as shown. 42 indicates a port-hole orinspection glass 'in the top of the secondary tank 30. 43 indicates awaterY jet or spray to which water is supplied by pipe 44 that iscontrolled by valve 45, for washing the underside f the glass 42 46indicates a gauge glass on the tank 3D. rA protected electric'light 41mayA be located within the tank adjacent the port-hole glass 42 toillumine the contents of the tank for better view thereof through theport-hole.

50 indicates baffling means within the main tank I0 forming a. ring-likeor annular eilluent take-off system for the main tank, for shielding thewithdrawn liquid from descending or settling solids at the place ofwithdrawal of the eilluent liquid from the liquid body in the tank. Thisis preferablyprovided with a downwardly inclined top member 5I, acylindrical member 52, a horizontal closure member 53 having apertures54 therein located at intervals. 55 indicates a treated liquid, oreilluent take-off discharge pipe valved at 55' that is provided with abarometric or hydrostatic leg 56 that dips into a basin or pool 51formed by means of an adjustable dam or Weir 58, over which liquid flowsto discharge through effluent discharge pipe 59.

Fig. 1 shows an 'optional assembly of sediment or sludge rakin'gmechanism, supported from and rotating with the draft-tube I8. Itcomprises rake arm 63 extending generally outwardly from the draft-tubeI (and, if necessary, braced with tie rods as shown) that are providedwith sediment or sludge impelling or plowing means such v65, from whichsediment can be discharged through pipe 66 and pump 61 ldownwardlythrough pipe 68 leading to a no-pool part 12 of lthe depressed sump 69.

' polluted liquid supplied for treatment. This pipe 16 delivers theliquid into a. wet-well or sump 11, wherein the liquid passes under anadjustable curtain baille 18. 19 indicates a gassi'ng station or gasdiffusing means-for causing gas or air to be dissolved and entrained inthe incoming liquid. In the drawing it is shown as a diusing or gassingimpelle'r on a shaft driven by a motor 6D.

8| indicatesy a, de-aerating or de-gassing flowthrough passage orchannel, in which there isA an adjustable height weir 62'ove'r which theliquid cascades before entering the Vacuator feed pipe I9. Thispassageway 8| is for de-aerating the liquidto rid it of enlargedentrained gas bubbles.

vlo

33 indicates a cover on the de-aerating passagel way to make theapparatus sightly. 84 indicates agate valve and means for operating itto open or close the entrance to the feed pipe I9. B5 indicates ajunction box and 86 a pipe, whereby the newly incoming liquid can beby-passed around the Vacuator, if desired, since the pipe 86 joins intothe sump 81, that is adjacent the pool 51. The discharge line 4I fromthe vacuum pump 35 all liquid isdiscarded through pipe 59.

Y 9D represents a manhole cover in the top I2 of the tank I0 forentrance. purposes.v 9| indicates an electrical light for illuminatingthe interior of the tank l0. 92 indicates.aglass-bearing porthole in thetop of the tank I0 for visual inspection purposes, and 93 indicates awater jet or nozzle, supplied from pipe 94 with its valve a5, forwashing scum from the underside of the glass of the port-hold 92.

It is to be observed that the inlet pipe I9 to the tank I0 has ,as itsvertically-extending terminal the draft-tube .I8. Under thosekcircumstances` where it is desired to have the drafttube rotatable,there is provided a liquid-tight slip-'joint as at 95 whereby the lowersection of the rotatable draft-tube can rotate freely around thestationary upstanding' end of the pipe I9 without loss of liquidtherebetween.

|00 .representsl a pipe or conduit for conducting gas, to the gassingstation 19, if|desired inr stead of air, to be diffused in the liquidbeing treated, a gas such as CO2 that is inert to an oxy' gen demand ofthe liquid.'

- The operation of the Vacuator is as follows: the incoming new liquidto be treated therein first is to have gas, such as air, diffusedtherein. This is done in a gas-dissolving station, in the embodimentillustrated by means of usual aeration by the use of an aeratingimpeller IGI. Thereafter, the larger. bubbles, and at least someentrained air, are de-aerated from the liquid in the passageway 8|. Thegassed and cie-aerated liquid then passes through the feed pipe I9 andupwardly inthe draft-tube I8 due to the eiect of vacuum within the maintank I0. There is maintained within the tank lIII an ever-changing bodyof liquid being treated, which reaches to a liquid level LA that iscarefully controlled by meansv of the control assembly 30. The liquidrises in the control or secondary tank or compartment 3U through thepipe 33. The vacuum pump 35 in 4exerting a gas-exhausting suctionthrough nozzles 31 on the interior of the secondary tank 30 5,5` abovethe liquid level L therein also produces a vcorresponding effect ofvacuum in the upper section of the main tank I0 that is above its liquidlevel L, through the medium of thev freely comlmunicating passageway orpipe 3l that extends between the upper sections of the main andsecondary tanks.

The liquid level L in the secondary tank 30 is controlled through'theadjustment of the nozzles 31, for the pump 35 is a wet-vacuum pump.

.65 If the liquid level tends to rise about the level of the nozzles 31,liquid is pumped therethrough until the liquid level in both tanksreturns' to normal. Any liquid sucked up by the pump 35 isdiscardedthrough pipe 4I. It is to be noted '-70 that the minor body ofliquid being treated that is hydrostaticallycontained withinV thesecondary tank 30 is shielded from having any scum or floating materialreaching it, because it is connected to the main tank at a point belowwhich the scum has been released.

also discharges into this sump 81, from which,

the tank at a, diminished velocity. due to the flare 2li of thedraft-tube I8. The velocityis diminished so that there is substantiallyno turbulence created above the draft-tube and its' `tends to shakebubbles loose from the solids to which the bubbles have become attached.As soon as the liquid is released from the drafttube I8. the lessenedpressure or effect of vacuum, causes' the dissolved and ilnely dividedentrained gas in the liquid to come out vof the solution, -whereuponlbubbles of gas are developed that cling to' suspended solidsencountered by the vgas bubbles. In sewage and the like wastes, there isenough oil and'grease on the suspended solids to'act as an adhesive tocause the bubbles to adhere to the solids, whereupon the bubbles causethe solids to whichthey are attached to be buoyed up-and to float to theliquid level L. Accumulation of the floated solids forms a floatinglayer of scum.

It is desirable to continually. remove the scum to leave the liquidlevel as free thereof as possible. To this end, the scum arms 26 arerotated with shaft 22 from motor 26. 4The scum arms with their sweeps 26push scum in front of them until the ramp 21 is encountered, when thesweeps 21 in riding up onto the ramp, push the scum before them, and.over the scum dam I6. The scumI falls from or cascades over the daminto the funnel section I6 of the scum removing ductmeans that includesthe pipe IB, through which pipe plus its barometric leg'll, the scum isdischarged from the main tank Il) and intothe pool ,or basin 1| `in amanner which prevents any air leakage into the tank Ill to otherwisespoil or diminish. the vacuum therein. l

`Liquid from which the oated material has been removed, is discardedfrom the tank as treated liquid or einuent through the eiiiuent take-oilassembly 50, byrising upwardly through the apertures N into the annular.baiiied space,

from whence it flows to discharge through pipe v 55. whichvalso is abarometric leg since it terminates in pool 61, to prevent air leakageinto the tank I0. The assembly 6l shields the drawnoiI eilluent fromvdescending'or settling solids,

and the assembly is located at a depth in the tank at` which the effectof vacuum is equal to the order of inches of mercury. 'It is the placevor region where there is a minimum of suspended solids and a minimum ofsedimented solids. In

g those cases where the Vacuator is to be used'only to de-scum theliquid to.be treated, the eilluent take-off will constitute the onlyother discharge duct from-the tank besides the scum removal duct. Insuch an instance, the eiiluent liquid will have entrained in it, thosesuspended solids. that have escaped or been immune to the flotationeil'ects of the vacuum. l

However, in other cases, it will be desirable to make a furtherseparation by riding the eilluent liquid of its suspended solids thathave escaped the vacuum notation. 'Ihis can be accomplished.

Liquid passes'up the draft-tube in the main'v tank I0 and is emittedinto the body of liquid in m action, is desirable as turin theembodlmentof the invention shown because the suspended solids that have escapedotation will descend and settle on the floor Il of the tank In bysedimentation processes, and will 5 accumulate as sediment on the iioor.The sludge rakes 64 in being moved at speeds that have a substantiallynon-rolling eiIect on the sediment, v l

by the traveling rake arms 63 due to rotation of the shaft 22 anddraft-tube l6,'wil1 impel the sediment inwardly toward the centerof thetank III until the sediment reaches the sludge sump 65, -from whence thesediment or sludge can be removed by the pump 61 and discarded through 4pipe 68 into the sump 12. In such a case, it can be seen that thesediment and the eiliuent liquid are discharged from Athe tank I0 byseparate and independent paths. The level at which the eiiiuent take-ofiis located is deep enoughin the tank to be at a point where the effectof vacuum is so slight that practically all floating material isthereabove, for it is quite important that no, or

substantially no, oating material pass from thev tank with the treatedeiiiuent. More particularly, the location of the eflluent take-offshould be suniciently below thellquid level of the tank that the effectof the vacuum at that take-oil? level is less than or equivalent to notsubstantially moreA than 5 linches of mercury. Since the feed to thevacuator is continuousand the scum and so' tion of the machine iscontinuous, and the liquid being treated in the vacuator is anever-changing body of liquid. Thesludge can be taken out trolled by theadjusted height of the suction noz-A zles 21 in the secondary tank orcompartment 3|), by the adjustment of the nozzles 31, the liquid levelin the tank Ill can be raised or lowered rel-1 atively to the height ofthe scum overflow dam l5. Ii the discharging scum is desired to bedewatered as much as possible, then the .liquid level is droppedsomewhat below the scum dam I6. On

' the other hand, in Aorder to make the discharging scum more iluid, itmay be desirable Ato have more water go out with it, in which case theliquid level in the tank I0 is raised with respect to the scum dam, bymeans of suitable adjustment of the pivvoted vacuum suction nozzles 31.

A Vacuator may be looked upon as an emcient substitute, at least in manyinstances, for a pres- '50 ent-day mechanically-cleaned clarifier, forexperience has shown that a Vacuator is effective `,in ridding theliquid being treated of a substantial lportion of its suspended solidsin about the proportion of 75% of floated suspended solids and 25%ofsettled solids. When the grease or oil content of the liquid is high,the floated solids removal is higher than otherwise. Further, the sludgedischarging from a Vacuator is cleaner in that it has fewer, smaller andlighter particles entrained in it, for the sludge has in eiIect beenexposed to what may be called a washing treatment. In a clarifier, thedetention capacity is from one to three hours, whereas goed results havebeen obtained in a Vacuator having only threeminutes detention, althoughfrom one to the eillue'nt take-offs are continuous, the opera-l From thesump 12 the mixture of discharged -v creased.

Vcompared with an ordinary clarifier.

'Initial operation for starting up a Vacuator 1 can be carried out byone of two methods. The

Preferred method'is to close-all valves 84 and 55' n on the'inlet andoutlet piping respectively so that the tank Ill can be filled by a pump(not shown) When the water level reaches the elevation of the scum damI5, the pumping can be discontinued,

the air-outlet connections closed to wit, air out-` flow pibescontrolled byvalves lll' the vacuum -pump 35 started, and as soon as thevacuum sauge used in connection with the pump 3i registers equivalent-to the hydrostatic leg in the tank, valves 8l and 55 in the inlet andoutlet piping respectively can be opened simultaneously, and flowthrough the inverted slphon I9 and I8 will automatically start.Obviously all hydrostatic legs must be kept sealed with liquid.

The respective water levels in the feed and effluent compartments willautomatically adjust themselves, depending upon the loss of head throughthe unit and the elevation of the overflow weir in an etlluent box.

The other method of starting consists in maintaining sumcient water inthe boxes or pools in which the hydrostatic legs are located, startingthe vacuumpump and thus pulling the water up into the tank as theabsolute pressure is de- For shut-downs of several hours duration, allvalves in lthe inlet and outlet piping can be closed when the flow hasstopped, and the vacuum pump can then be shut down without emptying thetank contents. For shut-downs of longer duration, the device can beemptied by stopping the vacuum pump and admitting air slowly through asuitable valve in the tank cover.

The normal adjustments obtainable during regular operation consistsprincipally of:

1. Control of water level elevation; and

2. Speed variation of skimmer mechanism.

, If for instance a material being handled forms a thick compact scumand vit is desired to discharge this scum with a minimum water content,then the water level in the control box should be adjusted by raising orlowering the nozzle to an elevation several inches below the scum dam.If, on the other hand, the material handled does not form a compact scumor its water content is not important, the water-level elevation canthen be. adjusted to substantially that of the scum dam so that most orall of thescum will flow into the scum outlet by gravity. In someextreme or unusual cases it may be advantageous to raise the water level'above the scum dam.

The presence of finely-divided gas bubbles in sewage or other liquid hasa decidedly detrimental effect on clarification by sedimentation; so

` to'rid the sewage of its entrained gas, substantially facilitates thesubsequent sedimentation.

And again, assewage and the like wastes are usually highly odorous. thevacuum removal of this invention rlds the liquid of its entrained gases65 and thereby reduces their odor-giving content.

In the gassing, or diffusing of a gas in sewage, it has beenV found thatsewage and certain other polluted waste liquids, have an loxygen demand.This is commonly referred to as B. O. D., which is an abbreviation ofbiochemical mgen demand.

If one attempts to diifuse air in such a liquid. the

` oxygen demand is so great that instead of the air being dissolved orentrained in the liquid. the oxygen of the air enters into chemicalcombination, with the result that when the aerated liquid gets into thescum flotation apparatus, ythe lessened pressure onthe liquid fails todevelop' gas bubbles as it would, due tothe air c'om'ing out 'ofsolution-and entrainment.l Consequently, it is proposed by thisinvention, in connection Iwith oxygen demanding liquids, to practice thegassing step heretofore described, by the'use of lsome gas that is inertto the oxygen demand of the liquid. For instance, in ythe treatment ofsewage, itA has been found that the gassing step can be satisfactorilycarried out by the use of carbon dioxide (CO2) gas. This has theadvantage not only of being readily soluble in the l sewage liquid, butupon encountering the lessened' pressure, due to the effect of vacuum inthe scum oating apparatus, the C0: comes out of solution and develops amaximum of very small bubbles, that are highly eifectlve for flotationpurposes.

Since the solubility of nitrogen in water is twice that ofoxygen, it isindicated that a nitrogen bearing gasvcan well be used. Of course, ifthe gsssmg be. donewitn a gas .other thansmtng gassing must be done in amanner so that the gas is not allowed to be wasted, so under suchconditions, the gasing station 19 would have* to be provided with a pipeor duct |00 that conveys the COz'or other inert gas for release directlyinto the agitation zone of the aerating or gassing element I9. The pointof this feature of .this invention is the supplying, to an oxygendemanding liquid, ofa gas that is inert to the oxygen demand or theliquid. Maximum solution and entrainment of the gas in the liquid isdesired with a minimum of chemical reaction of with the liquid.

We claim: l. The process of removing suspended solids from theircarrying liquid which comprises mainthe gas from the surface of the bodyat a point functionally remote 'from the point or application of thesuction. and continually removing from the body clarified liquid.

1 2. The process ol' removing suspensions from a liquid bearing'themwhich comprises establishing and enclosing liquid divided into a majorliquid body and a minor liquid body with both bodies havingv a commonatmosphere and with liquid inthe minor body having a verticallyfluctuatlns liquid level, Supplying feed liquid to the majorbody,-removing floating scum from the major liquid body, dischargingeilluent from the enclosed liquid from a place functionally remoteAAfrom the oating scum, sucking liquid from the minor body when the liquidlevel thereof rises above a predetermined elevation, and sucking gasfrom above such liquid when the liquid level thereof falls below suchpredetermined elevation. 3. Apparatus for the removal 0f suspensionsfrom a liquid bearing them which comprises a closed tank adapted toh'old a liquid body whose taining an enclosed body or liquid beingtreated removing means adapted to pump liquidthrough the suction meanswhen the liquid level rises thereabove and thus controlling the liquidlevel of the tank. and means for removing treated liquid from the tankhaving an inlet in the tank `that is disposed functionallyA remote fromthe inlet to the floating material removing means.

4. APPBlatus according to claim 3, including means providing an vauxiliary compartment as sociated with the tank for holding in its lowerportion liquid derived from the liquid of the tank and having itstopportion in gaseous communication with the space above the liquid inthe tank. with the addition that the inlet of the suctionv means isadjustable and is associated with th'e auxiliary compartment forcontrolling the liquid level of the liquid therein.

5. Apparatus for the removal of suspensions from liquids comprising aclosed ytank adapted to hold a liquid body having a normally verticallyfluctuating liquid level, tube means by which gassed liquid may be fedintothe tank and delivered in the region of the surface level of theliquid in the tank, comb d wet and dry suction means adapted tomaintainsub-atmospheric/ pressure within the tank including a pipehaving an inlet disposed within the vertical limits of they iluctuatingliquid level, and a pump connected with said pipe e'ective to drawliquid therethrough when the inlet is submerged and to draw gastherethrough when the inlet is unsubmerged,

a scum-discharge duct leading from the tank including a liquid sealthereon exteriorly of the tank, means for sweeping floating scum intothe scum duct, and means for conducting treated liquid vfrom the tankincluding a liquid-sealed lower end outside the tank. l 6. Apparatusaccording to claim 5 with the addition of av dam' provided at the upperintake end portion of the scum discharge duct over which iloatingmaterial must pass before entering said duct. and wherein said suctionmeans includes adjustable means for varying the liquid level relative tothe dam. l 4'L Apparatus for removal of impurities from liquidscomprising a closed tank adapted to hold a liquid body, tube means isbywhich gas-containing liquid may be fed to the tank and delivered at thelregion of the liquid level in the tank, suction-producing means formaintaining vaca uum within the tank, --a- 4scum-discharge ductincluding a dam at -the upper end thereof and having a. liquid-sealedlower end, means for sweeping floating material in the tank over the damand into the scum duct, means for removing treated liquid from the tankat an elevation lower than that of said dam and having a liquidsealedlower end. said suction-producing means having a positionable suctioninlet disposed at l an elevationvproximate to that of the upper edge lsavor rated fromA the positionable suction inlet.

9. Apparatus for removal of suspended matter .I from liquid comprising atank adapted to hold -a main body of liquid being treated, tube meansleading into the tank ,and 4having a terminal from which gas-containingliquid being treated is delivered within the tank, means for maintainingadjacent the main liquid body a second body of liquid whose liquid levelis subject to atmosphere with the main body, means for connecting theatmosphere of the second body with that-of the main body, meansproviding a pas'- l5 rial floating on the-main body, means for removingtreated liquid from the g tank, and suction means essentially embodyinga gas-liquid pump and a pipe having an inlet disposed cooperativelywithin the vertical limits of the fluctuating level of the second liquidbody serving for alternately withdrawing liquid through the pipe inletwhen submerged and gas when unsubmerged for thereby controlling theliquid level of the second liquid bodyas well as gfor applying vacuum tothe comf mon atmosphere of the main and second liquid bodies. 10.Apparatus Vfor the treatment of (liquids having suspensions thereinwhich comprises a closed tank adapted to hold liquid with at least laportion of which whose liquid level uctuates vertically. tube meansterminating inthe tank -for supplying gas-containing feed liquid there--to, scum-receiving means having an inlet disposed to receive oatngscum, means for passing `scum fromv the tank through said receivingmeans 'whileminimizing leakage of air there- 4 having an inlet disposedfunctionally remote from the scum inlet but within the range ofiluctuationsof the liquid level for sucking liquid whenthe inlet issubmerged and gas when nonsubmerged whereby sub-atmospheric pressure is'maintained on the tank liquid, effluent discharge conduit means leadingfrom the tank having an inlet seetion'that `is disposed functionallyremote from the scum-receiving means, liquid-seal means exteriorly ofthe tank associated with thev eilluent discharge means for minimizingleakage of air therethrough, and means for shielding from suspended andsettling solids the inlet section of the conduit means. l 11. Vacuumflotation apparatus comprising a closed tankadapted to hold a body ofliquid therein having a liquid level, feed inlet means having arotatable feed-emission terminal and a fixed delivery section leadingthereto vby which gas-containing liquid suspension is fed into the tankand released into the liquid body at the region of the surface levelthereof` suction means for applying sub-atmospheric pressure to thesurface of the liquid in the tank, a -scum-discharge duct leading fromthe tank proximate to the liquid level therein, means for sweepingoating scum thereinto, 'a motor-driven shaft extending vertically intothe tank, conduit means leading from the tank for conducting treatedliquid therefrom, independent liquid-seal means ported and rotated fromsaid shaft, and the scumv l the noot-sweeping means is functionallysepavertical fluctuations and which has a. common sageway for flow ofliquid from one body to the other, means forv removing from the tankmatethrough, suction means leading from the tank forv the. scum duct andfor the conduit means sweeping means being also from said shaft.

12. An apparatus for `performing a continuous process for separating andremoving oi' suspended matter from a liquid which comprises a closed topmain separating tank adapted for the establishment therein 'of anever-changingm'ain body of liquid for treatment normally maintained at apre-determined liquid level and of a gas-holding portion that directlyoverlies said liquid body whose pressure is maintained substantiallyVlower than vthatof the outside atmosphere; means providing an auxiliaryliquidheight control compartment having a 4lower liquideholding portionadapted for the establishment therein of an auxiliary body of liquidderived from the mainv tank and an overlying gas-holding portion; meansdefining a freely communicating gas passageway between said gas-holdingportions; pumping means for resupported and rotated means the normalliquid level'of the body of liquid in the main tank and alsoto removeany liquid tending to rise above thel so-e'stablished normal liquidlevel; means for continuously submergedly delivering a liquid-solidssuspension into the main tank while permitting no substantial leaking ofoutside air into the main tank; meansA for continuously releasing liquidfrom the main tank without permitting any'substantlal leakage of outsideair into the main tank; an open top'trough located within the main tankhaving a horizontally extending transfer edge at an elevation proximate,that of the nozzle intake means; and means for transferring materialfrom said open top trough to the exterior of the apparatus withoutpermittingany .substantial leakage of outside air into the tank.'v

moving gas from said gas-holding portions and adapted for maintainingsubstantially sub-atmospheric pressure conditions therein and oomprisingon the intake side thereof pipinghaving 13. An apparatus according toclaim 12, also having means for impelling floatable matter from thesurface of the body of liquid in the main tank towards and over thehorizontally extending transfer edge ofthe trough and thus into the openmp trough.

EARL M. KELLY. ARTHUR .maar ROBERT '.m'rE.

ELLIOTT J'.` ROBERTS. DAVID B. SUTHERLAND.

